The diagnosis of ALS can be difficult since its symptoms are very similar to various other diseases/disorders such as those listed below:
Using these techniques, most cases of ALS are readily diagnosed. In large ALS clinics error rate in diagnosing ALS is less than 10%.
- Viral infectious diseases
- Human immunodeficiency virus (HIV)
- Lyme disease
- Syphilis
- Neurological disorders
- Spinal muscular atrophy
- Post-polio syndrome
- Electromyography (EMG) - This test involves the use of an instrument called an electromyograph which produces a record called a electromyogram. The record shows electrical activity in the muscles. Specific EMG signs can support the diagnosis of ALS.
- Nerve conduction study (NCS) - The NCS is used to check if the motor and sensory nerves can electrically conduct signals. One of its key parts is measuring the nerve conduction velocity (NCV) of different nerves. NCV is the speed at which an electrochemical impulse travels down a neural pathway. Certain abnormalities in the NCV results may suggest that a person has peripheral neuropathy (damage to peripheral nerves) or myopathy (muscle disease) as opposed to ALS.
- Magnetic resonance imaging (MRI) - This is a medical imaging technique used to scan the body for abnormalities. MRI scanners use strong magnetic fields, radio waves and field gradients to make images of the body. A person in the early stages of ALS will generally seem normal from a MRI scan but the scan can reveal if the patient is in fact suffering from spinal cord tumor, multiple sclerosis (myelin covering nerve cells is damaged), syringomyelia (a cyst forms within the spinal cord) or another disease with similar symptoms.
- Blood/Urine test - Taking a sample of the patient's blood/urine may show if the patient is suffering from another disease with symptoms similar to ALS.
Using these techniques, most cases of ALS are readily diagnosed. In large ALS clinics error rate in diagnosing ALS is less than 10%.